Investigation of the Upper Critical Magnetic Field and Activation Energy in MgB2 Thin Film

Koparan E. T., Surdu A., Sidorenko A., Yanmaz E.

JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM, vol.25, no.7, pp.2235-2238, 2012 (SCI-Expanded) identifier identifier


MgB2 film with a thickness of about 600 nm was deposited on the MgO (100) single crystal substrate using a "two-step" synthesis technique. First, deposition of boron thin film was carried out by rf magnetron sputtering on MgO substrates and followed by a post deposition annealing at 850 A degrees C in magnesium vapor. The upper critical field H (c2) has been estimated from temperature dependences of resistivity curves in both directions of the magnetic fields perpendicular and parallel to the c-axis. Resistivity measurements of the film were performed using a standard four-probe method under different magnetic fields up to 70 kOe in zero fields cooling regime. The upper critical magnetic field H (c2)(0) at T=0 K for 90 % of R (n) was calculated by the extrapolation H (c2)(T) to the temperature T=0 K. The results showed that H (c2)ayenab(0) and H (c2)ayenc(0) was found to be around 22 T and 18 T, respectively. Using extracted data, the zero-temperature coherence lengths and field anisotropy ratio were calculated. In order to determine the activation energy of thermally activated flux flow of the film, Arrhenius law was taken into account.